Linux: Where Are Environment Variables Stored

Linux: where are environment variables stored?

The environment variables of a process exist at runtime, and are not stored in some file or so. They are stored in the process's own memory (that's where they are found to pass on to children). But there is a virtual file in

/proc/pid/environ

This file shows all the environment variables that were passed when calling the process (unless the process overwrote that part of its memory — most programs don't). The kernel makes them visible through that virtual file. One can list them. For example to view the variables of process 3940, one can do

cat /proc/3940/environ | tr '\0' '\n'

Each variable is delimited by a binary zero from the next one. tr replaces the zero into a newline.

Where are environment variables of a process is stored in linux?

On modern Linux systems, environment values are "kind-of" stored on the stack -- for specific values of "kind-of".

The actual strings that make up the environment are stored at the top (highest-numbered addresses) of the process's virtual address space, along with other environmental data. The stack proper begins immediately below this. The addresses of the individual environment variables are pushed onto the stack by the kernel's program loader, along with the argc and argv values.

This close correspondence between the environment and the stack leads many writers to talk about the environment being "on the stack" although, strictly speaking, only the addresses of the specific environment values are properly on the stack. Diagrams of the Linux process address space often show the stack at the top of memory, although if you run pmap on a process, you'll see that this isn't usually the case -- there will be one or two segments above the stack proper, and the environment variables will be found in one of these.

Where are environment variables stored in node.js?

As pointed in the comments, you have to provide these variables while invoking your node program:

$ NODE_ENV=test node yourApp.js

And you can access this in your code as:

console.log("Environment variable: " + process.env.NODE_ENV);

What are my environment variables?

I am not sure if thats what you want, but try printenv

This will show you all your environment variables.

About where they are stored

Linux: where are environment variables stored?

How to set Shell Environment Variables

http://www.codecoffee.com/tipsforlinux/articles/030.html

Happy reading :-)

Where are all the places where an environment variable can be set in linux?

As I commented, use

grep -rl VARNAME /etc $HOME

to ask grep to recursively (-r search in file trees recursively) search and list filenames (-l ask grep to just list matching filenames) containing the pattern VARNAME inside /etc (the system-wide configuration directory) and inside your $HOME

where Environment variables for python are saved

Environment variables live in the memory, not on the disk. People usually save environment variables in files only for not having to do the same exporting of them by hand repetitively.

Also note that, environment variables are properties of operating system processes, and the process specific ones are passed on to all of the subprocesses of that process.

So when you run os.environ, it shows the environment variables and their values belonging to the python process (the executable that is being executed).

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